Roof-topping enthusiast Daniel Lau takes a selfie with high-rise buildings down below as he stands on the top of a skyscraper in Hong Kong, China on August 15, 2017. A craze that began in Russia has now taken hold in Hong Kong, one of the world's most vertical cities. Mr Lau said he had been inspired by Russian climbers and that he was unafraid of the vertiginous heights he scales. (Photo by ImagineChina/Rex Features/Shutterstock)

Serra da Aboboreira Megalithic Set (Meninas do Crasto) on September 24, 2023 in Baiao, Portugal. Since 1978 that Serra da Aboboreira (Aboboreira Mountains) has been the scene of a systematic study of its archeological values, among which are the monuments known as megalithic. These are funerary monuments designing the landscape. These dolmens were constructed with stones (lithos) of medium or large dimensions (mega), which were laid in a, more or less, vertical position. Over these, it was still placed a lid, also of stone. These containers were covered by an artificial mound of earth and stones (dolmen). (Photo by Octavio Passos/Getty Images)

Jacob's Well is a perennial karstic spring in the Texas Hill Country flowing from the bed of Cypress Creek, located northwest of Wimberley, Texas. The twelve foot (four meter) diameter mouth of the spring serves as a popular swimming spot for the local land owners whose properties adjoin Cypress Creek. From the opening in the creek bed, Jacob's Well cave descends vertically for about thirty feet (ten meters), then continues downward at an angle through a series of silted chambers separated by narrow restrictions, finally reaching a depth of one hundred and twenty feet (forty meters). Until the modern era, the Trinity Aquifer-fed natural artesian spring gushed water from the mouth of the cave, with a measured flow in 1924 of one hundred and seventy gallons per second (six hundred and forty liters per second) discharging six feet (two meters) into the air. The spring is the greatest source of water recharging the Edwards Aquifer.

Singers “Elle & The Pocket Belles” attend day 3 “Ladies Day” of the Qatar Goodwood Festival on August 3, 2017 in Chichester, England. (Photo by David Hartley/PA Wire)

A woman travels on a train stopping at a subway station visited by foreign reporters in central Pyongyang, North Korea on April 14, 2017. (Photo by Damir Sagolj/Reuters)

The May Queen during the Beltane Fire Festival in Edinburgh, Scotland on April 30, 2022. A dynamic reinterpretation of an ancient Celtic celebration of the return of summer, the festival is centered around the story of the May Queen and the Green Man, and the lighting of the Beltane bonfire, symbolic of purification, healing and new life. Edinburgh's Beltane celebrations are the largest of their kind in the world with around 250 volunteer performers and thousands of spectators. (Photo by Jane Barlow/PA Images via Getty Images)

Pinky Ghelani and Suzzy Wokabi watch a TV broadcast of Britain's Prince Harry and Meghan Markle's royal wedding at the Windsor golf and country club in Nairobi, Kenya May 19, 2018. (Photo by Thomas Mukoya/Reuters)

A tear rolls down the cheek of Karima el-Mahroug, also known as Ruby, a Moroccan woman at the center of ex-Premier Silvio Berlusconi's s*x-for-hire trial, as she reads a statement to reporters during a protest outside the court house, in Milan, Italy, Thursday, April 4, 2013. The Moroccan woman at the center of ex-Premier Silvio Berlusconi's s*x-for-hire trial has denounced what she says is psychological warfare being waged against her by Italian prosecutors. Ruby, read out a lengthy statement Thursday to a gaggle of reporters in front of Milan's courthouse denying she was a prostitute and insisting that prosecutors hear her side of the story. (Photo by Luca Bruno/AP Photo)